In systems which provide for a plurality of remote zone sensors to be monitored at a central controller, a variety of techniques have been heretofore employed for communicating between the central controller and the remote zone sensors. In some of these systems, individual wire have been run from the central controller to each of the remote zones and, in others, a single two-wire communication cable has been used which may employ frequency or time division multiplexing. Although the use of a single two-wire communication cable is preferable because of the saving in wire and labor, the state of the art multiple-zone sensor intrusion detection systems of this type offset some of this saving by employing costly, bulky, and/or low performance zone transponders. It is highly desirable, therefore, to provide a multiple-zone intrusion detection system that utilizes a single two-wire communication cable wherein the zone transponders therefor are simple, small in size, have performance equal to individually wired zone sensors, and, yet, are relatively low in cost.